Q: Can you use the Skullduggery promo card to cancel a Plunder – not on the Rule itself, but on a single act of Plundering?

Or to cancel City Of Thieves in Adventure Time Fluxx, or Fantasy Fluxx, or Crime Happens in Batman Fluxx, or the Rule of Acquisition in various Star Trek Fluxxen

A: Yes. That’s what it was originally designed for!

(Note that if you stop Acquisition from happening, you don’t get to take a card from the Acquiring players hand either. The entire card play is canceled.)